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  Atomic Number of the Element with Lowest First Ionisation Enthalpy | JEE Chemistry 📌 Question The atomic number of the element from the following with the lowest first ionisation enthalpy is: 📚 Concept Used – First Ionisation Enthalpy Definition: First ionisation enthalpy is the energy required to remove the most loosely bound electron from an isolated gaseous atom in its ground state. Periodic Trend: Across a period → IE increases (nuclear charge ↑, atomic size ↓) Down a group → IE decreases (atomic size ↑, shielding effect ↑) Lowest IE Element: The element at the bottom-left of the periodic table has the lowest IE, because it has large size and weak nuclear attraction for the outermost electron. 🖋 Solution The element with the lowest first ionisation enthalpy is Francium (Fr) , but in practical chemistry, Cesium (Cs) is often considered because Francium is radioactive and rare . Francium’s atomic number = 87 Therefore, the answer ...

     🧲 Solutions  | Chemistry  |  Doubtify JEE 🧮 Question: The density of the NaOH solution is 1.2 g/cm³. What is the molality of the solution? 🖼️ Question Image: ⚗️ Concept Overview: This is a fundamental problem from the Solutions chapter of Physical Chemistry. It tests your understanding of molality , density , and the method of converting between different concentration units. In many JEE Main and Advanced problems, students get confused between molality (mol/kg) and molarity (mol/L) . This problem helps to eliminate that confusion and improve conceptual clarity. 🧠 Step-by-Step Explanation: Let’s assume we are working with 1000 cm³ = 1 L of NaOH solution. Density = 1.2 g/cm³ So, total mass of 1 L solution = 1.2   g/cm³ × 1000   cm³ = 1200   g 1.2 \, \text{g/cm³} \times 1000 \, \text{cm³} = 1200 \, \text{g} Let’s say the solution is x% NaOH by mass (you may be given the percentage or molarity in the full version of the question – for no...